How to make resin coasters – resin coaster tutorial

Originally written July 2016.  Updated December 2019.

by Kate Ledum

If you are looking for an easy and fun way to make a handmade gift, then making resin coasters is for you!  Making small resin charms from other projects, then including them in a new project like this resin coaster DIY, is a great way to double the handmade fun.  This project is going to show you the fun of using resin leaves and shells you have already made in how to make resin coasters.

And don’t worry if you are asking yourself how to make resin coasters without making your own resin charms.  You can do it with found objects as well!

In the article Using Pearl Ex with Resin Two Ways we made a variety of resin leaves. We also made some shells using the same techniques. These are both perfect for including in a resin coaster.

Other small castings such as butterflies, ballerinas, flowers, and buttons will work great too. The items you include in the coaster should be no more than ¼” thick. The items will also need to be smaller than the coaster mold. If you’re putting in multiple items, 1-2” or smaller are recommended. The mold we’ll be using is 4” in diameter and 3/8” deep.

Deciding Which Way the Coaster should face

The first thing you do for a project like this is to decide which side you want to be the top of the coaster. If you want the side facing the table to be the top, you will need to put everything in upside down. Otherwise, if you want the side facing you to be the top, then everything will be facing up. Everything facing you can be easier to arrange since you can see exactly how it is going to look. With everything facing the table, you can lift up the mold and look at it from underneath, but that can be risky while you have liquid uncured resin in it.

The inner surface on this mold is not shiny. That means the finished item will have a matte finish except where the resin is poured in. The pouring side will have a shiny finish. Knowing how the finished item will be can also help you decide.

The coaster mold has a very gently sloped side making the diameter of the mold slightly smaller on the table side. If you make the coaster with the table side up, the top of the coaster will be slightly smaller than the bottom. If you make the coaster with the side facing you as the top, the top will be slightly larger than the bottom. Either way will work well as a coaster.

For this project on how to make resin coasters, the leaves coaster will face toward you and the shell coaster will face the table. For steps which are the same for both coasters, only the Leaves is shown.

Deciding What to Put In the Coaster

Place the the charms you want to use into the dry mold. See how they’ll fit and how you like them placed together.

TIP:  Since a coaster needs to be flat to do its job, you need to make sure all the items you put in the mold rise above the edge. One way to check this is to place a piece of paper across the top of the mold. As long as nothing is touching the top of the paper or poking it up, it should be fine.

TIP: You can take a picture of how you placed your items in the dry mold to use as a guide when putting them in with the resin later.

Prepare the Mold

Spray the mold liberally with the mold release and set it aside to dry for at least 30 minutes.

Prepare the resin and your work area

Before you start mixing the resin, you should put on a pair of protective gloves.

For the best results, resin likes a warm, but not hot room. 72-74F is the recommended temperature for how to make resin coasters.

Warming resin in a warm water will help reduce bubbles in the mix. You can use a bowl with very warm, not hot, water or an electric salsa pot for no more than 5-10 minutes.

Measure and mix the resin

The coaster mold we’re using holds a total of 2 ½ ounces of resin. I’m mixing a bit more than 3 ounces (100 ml) of resin for both of the molds. The marks on my resin cups are essential to making sure I get accurate measurements.

1. In one cup, pour in enough of Part A (clear liquid) to reach the 50 ml mark.
2. Pour 50 ml of Part B in a second cup.

3. Combine Part A and Part B.
4. Using a stir stick, scrape the sides of the cup while slowly stirring the resin to mix the parts. This helps to reduce the number of bubbles in your mix.
6. Scrape the side of the cup and stir stick from time to time.
7. Mix until everything goes clear, which takes about two to three minutes.
8. Then pour the mix into a third cup and mix for at least 1 minute more to ensure all of the resin is completely mixed.

Pouring in the First Layer of Resin

Pour a small amount of resin into the mold.

To evenly coat the bottom of the mold, you can tip it slightly from side to side. At this point you want only about 1/8” to cover the bottom of the mold.

Adding the Leaves

For the leaves mold, we’re going to have the side of the mold facing up to be the finished top of the coaster. This means we’ll be placing the leaves so they’re facing us as we work.

Pour a small amount of resin into a small cup. Using a small cup for the next stage is much more manageable than a large one.

Drop one of the resin leaves into the small cup and spoon resin over it with the stir stick. Covering an inclusion with liquid resin helps to avoid trapping bubbles when putting it into the mold. The liquid on the inclusion will ‘meet’ the other liquid and flow together pushing away bubbles from under the inclusion. An inclusion is anything you’re ‘including’ in a resin casting. Resin leaves are the inclusion for this coaster.

Once it’s coated with liquid resin, pick the leaf up with your stir stick and slip it into the mold, into the thin layer of resin.

Be careful not to trap any bubbles beneath the leaf as you move it into position.

Add more resin leaves, first bathing each in resin. Use your stir stick to move them around in the mold as desired.

Continue adding leaves. If you took a picture earlier when you were dry fitting them in the mold, you can use it now to arrange them similarly. Push down the leaves to make as flat a surface as possible. Make sure you do not have any leaves poking up higher than the sides of the mold. You can use the paper across the top now, too, but be careful not to dip it into the resin. Getting resin on the paper won’t ruin the casting, but it will make your paper unusable.

Pouring on Additional Resin

After you have arranged the leaves, you want to pour in enough resin to cover them but not so much that it overfills the mold. Pour the resin to about 1/8” below the lip of the mold. Use your stir stick to push down any of the leaves that are too high or that might have decided to float.

Shells Mold

Going back over to the shells mold. For this mold, we’re going to have the side facing the table as the finished top of the coaster.

Repeat Step 5 above in our project on how to make resin coasters to add a thin layer of resin to this mold as well. For this mold, since we’ll be adding in some rounded items, make that first layer about 1/4” to have a bit more liquid for the shells to sit in.

Just as with the leaves, coat each shell with resin before you put it into the mold. Place the shells so their back is facing you. If you have other resin shells than the ones we cast in the first tutorial, you can add them as well.

Once you have the shells placed, like the leaves mold, pour in additional resin but stop at about 1/4” from the top so we can add a ‘sand’ level later. If any of the shells is above the line of the resin, when we add the ‘sand’, they’ll look sunk in a bit rather than sitting on the ‘sand’.

Popping Bubbles

To help reduce the inclusion of bubbles in the resin, you can use a heat tool (such as one used for heat embossing on cards) or lighter to encourage bubbles to rise to the top. Many bubbles will pop on their own. You might have to use a toothpick or the edge of a clean stir stick to encourage bubbles congregating on the sides to pop. When you have inclusions in the resin, it’s doubly important to follow this step as bubbles can get trapped in the shapes.

Just as with the leaves, coat each shell with resin before you put it into the mold. Place the shells so their back is facing you. If you have other resin shells than the ones we cast in the first tutorial, you can add them as well.

Leave to cure

Cover your molds and wait for the resin to cure. It is always best to cover your curing resin because you don’t want dust or cat hair or other unwanted things to become part of your project.

With Easy Cast, the cure time to unmolding is a minimum of 12 hours after the last resin was added.

Add Sand to the Shells Coaster

We’re going to give the shells some sand to ‘sit’ on. Since we’re building the coaster from the front to the back, we have to add the back when there won’t be any chance of it sinking down to become part of the front of the finished piece.

After the Shells coaster has been curing at least 4-5 hours (if you’re using Super Clear, at least 2-3 hours), the resin should be firm but can be sticky. This is a soft cure stage and a good time to add more since it will stay ‘behind’ everything we included earlier.

TIP: You can do this step after the first layer is fully cured for exactly the same effect. The two layers of resin will create a permanent bond.

Before adding the next layer is also a good time to flip over the mold and look through the clear plastic to get an idea how the coaster will look. Do not remove the coaster from the mold and be careful not to break the seal at this time. If there is air between the cured resin and the mold, the new resin will flow into that space and ruin the project.

To add another layer, we have to mix up a brand new batch of resin. Since this is going to be a small area, we can use the small cups and mix up just an ounce of Easy Cast. Make no less than the minimum recommended by the instructions that came with the resin.

Like we did before, pour a thin layer of resin on to the soft cured resin. Be sure to get the backs of each of the shells wet with the new resin. This will help reduce bubbles and get the next layer where we want it.

For this project, I was going to use real sand but didn’t have any on hand (or rather couldn’t find the sand I am sure I still have stashed somewhere) so I made faux sand from mixing a couple colours of Pearl Ex and adding in some chunky glitter. Real sand would work the same way as this faux sand.

Pour a small bit of the resin into another cup. You don’t want to just dump the sand into your main mixing cup because you want to have more control over how much resin and how much sand you’re combining. Plus, if you dump the sand in to the main cup, if you have resin left over, you can’t really do anything else with it.

Add the sand to the second cup and, with a second stir stick, slowly stir to combine the sand with the resin. Try not to introduce bubbles into the mixture. When the sandy resin is ready, it will look a lot like watery mud or a slurry.

Pour the sandy resin into the mold over the shells.

Continue filling the mold with sand and resin until it is about 1/8” from the top edge. This helps to avoid overfills. If there are still bits sticking up, don’t worry. There are a couple more steps left.

Just as before, use a heat tool to pop any bubbles and then set the coaster to cure

Removing the Coaster from the Mold

After more than 12 hours after the last resin pour, the coaster should be ready to unmold. Remember that we poured additional resin into the Shells coaster. It will be ready to unmold later than the Leaves coaster. When using Easy Cast, I usually wait until the next day to unmold.

Carefully bend the mold a little to start a line of air around the edge of the mold. You can press from the centre back of the mold as well. Continue lightly bending the mold until you can lift part of the coaster free. Because we used mold release at the start, the coaster should come out without a lot of effort.

When you bend a plastic mold to release cured resin, you don’t want to twist it so hard it bends out of shape, just enough to break the seal between the mold and the cured resin. Sometimes a whack on a hard surface, like a desk, can help break the seal, just like when you need to break the seal on a new jar of jam. A single whack is usually enough. If the seal still doesn’t want to break, you can put the mold with the stubborn resin into the freezer for 10-15 minutes. When you take it out, give it a whack on the counter or desk. Once you start to see a bubble of air between the mold and the cured resin, you’ve won.

Finishing the casting edge

When you cast in a mold and don’t fill to the absolute top of the edge or dome, the resin will cure ever so slightly concave. This will leave a sharp and potentially uneven edge all around that’s difficult to show in pictures but your fingers will definitely feel it.

You can carefully cut away the majority of the sharp edge with a sharp pair of scissors. The resin is pretty thin in this location and can be simply cut away. Make sure you cut around the mold evenly.

You can also sand the edge. A nail sander from the dollar store works great because it’s an easy shape to hold in your hand and the sanding surface is not too coarse. You generally don’t want anything coarser than 400 grit.

Be sure to wear safety glasses any time you are sanding resin. It’s also best to wear a paper breathing mask to avoid inhaling any of the resin dust.

Sanding the coaster

After taking off the edge, you should do a ‘tip test’ to see how flat the coaster is to determine what other steps we might need to do.

Put a water bottle or cup on the resin and try to tip the item from side to side. If it doesn’t rock, then the coaster is flat enough. If it does rock, you’ll need to do something to make it flatter, either add a small coating of more resin, similar to doming, or sand off the bits that stick out.  This is an important nuance in how to make resin coasters.

On the Shells coaster, a couple of the shells extend further than the ‘sand’ layer. This can be detected in the tip test and also just by looking from the side. Since the bottom of the shells are sticking out the back, let’s sand them down a bit.

When sanding a large area of resin, not only can it create a large amount of resin dust, but the friction can heat up the resin and cause some melting. Sand the coaster in a pool of water to accommodate this. A cheap foil pan works well.

WARNING: If any item is used with uncured or resin dust, it is unsafe to use it with food after.

To sand evenly, move it over the sand paper in a figure eight.  Check the edge to make sure it’s smooth to the touch as well..

Only sand to flatten on the back side of your coaster. If you need to flatten the top and want to preserve the inclusions that might be protruding a little, you can add a small layer of resin similar to a doming technique.

Adding a cork base to the resin coaster

Since the shells coaster of our how to make resin coasters project has an opaque bottom, this is a perfect time to add a cork bottom. It will also be less likely to scratch any surface. You could use felt for this instead if you prefer.

Trace the mold on to the cork with a pen or pencil and then cut it out on the inside of the line.

Slather the cork disc with craft glue. Be sure to get the glue out to the edges and not too thick.

Place the cork disc to the back side of the coaster and press firmly to adhere well.

Adding clear dots to the coaster base

After the leaves design of our how to make resin coasters project is fully cured, we can finish it, too.

To preserve the clear look of the coaster, we’ll add some clear dots to the bottom. This will help prevent the coaster from scuffing surfaces and keep it from moving. You can buy bumper pads at hardware or craft stores.  They are usually in the area of hardware for hanging pictures or cabinet doors.

Most bumper pads are self-adhesive. Simple peel them off and stick them where you want. Since I’m want a clear look on the leaves coaster, I placed them behind the opaque leaves. You want the pads to be evenly spaced so the coaster doesn’t rock when something is placed on it.

Finished resin coasters

Ta da! We now have two coasters from our how to make reisn coasters project made with resin items we cast earlier.  It was fun making two styles using the same coaster mold. This how to make resin coasters tutorial covered a lot of techniques too while learning how to make them.

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